It is important that the attachment of the cable be highly resistant to being pulled out, and also to the twisting of the cable on itself, repeated bending, and the risk of the cable being bent with too small a bend radius about its attachment. It is also important to provide sealing in contexts where there is a risk of ingress of moisture (or of any other gaseous or liquid corrosive atmosphere) into the housing, as is the case, for example, of a radiological sensor placed in the mouth of a patient.
It is not easy to design methods of attaching cables which allow all these constraints to be satisfied optimally.
In the prior art, a cable attachment was often reinforced by overmolding flexible plastic around the cable outlet, this overmolding encompassing both part of the cable and part of the housing. The problem with this overmolding was that it was bulky.
It is an object of the present invention to provide a method of manufacture that is more effective than those proposed hitherto for improving the robustness and other qualities (such as the sealing) of the attachment without thereby increasing the bulk thereof, bulk being critical in certain applications.
In order to achieve this, the invention proposes a method of attaching an electric cable, covered with a sheath made of a thermodeformable plastic, to an electronic circuit housing. A rigid bushing is fitting onto the stripped end of the cable having a hollow body, the inside diameter of which accepts the conductors but not the sheath of the cable. The bushing has a protruding collar at its end. The end of the cable and the bushing is fitted into a heated mold comprising a slightly conical interior surface part of a diameter smaller than that of the collar and a cylindrical part of a diameter larger than the large diameter of the conical part. The mold is heated to a temperature at which the material of the sheath will soften. The bushing is driven in the direction of the axis of the cable, so that the body of the bushing becomes inserted between the conductors of the cable that it surrounds and the softened sheath. The collar of the bushing is upset so that the material of the sheath to the point it fills the conical part of the mold. In order to solidify the sheath, it is cooled. The end of the cable is extracted from the mold. The end has a conical sheath portion of increasing diameter ending with the protruding collar. Another end of the cable is inserted, from inside the housing, through an opening in the housing, the diameter of which is very slightly smaller than the largest diameter of the conical sheath portion. The housing is closed.